1. Field of the Invention
The present invention relates to a starter having a shift lever for pushing out a pinion thereof, so that the pinion engages with a ring gear of a vehicle engine to start the engine.
2. Description of Related Art
It is known to provide such a starter with means for reducing wear of its shift lever as described, for example, in Japanese Patent Application Laid-open No. 2002-213329, and Japanese Utility Model Application No. 62-82365.
Japanese Patent Application Laid-open No. 2002-213329 discloses that a shift lever of a starter is formed with a hole at its end portion pressing an axially movable body, and this hole is filled by grease. The grease filled in the hole eases the friction between the end portion of the shift lever and the axially movable body, to reduce the wear of them. Japanese Utility Model Application Laid-open No. 62-82365 discloses that a shift lever of a starter is coated with a heat-resistant and wear-resistant material at its pinion pressing portion. This coating can reduce wear of the pinion pressing portion.
Incidentally, if such a starter enters the so called overrun state where a pinion of the starter is not pushed back by a shift lever after an engine is started, and accordingly the pinion continues to be engaged with a ring gear of the engine, a motor of the starter is caused to rotate at high speed by an engine torque. To avoid occurrence of such an overrun state, it is common that a one-way clutch is disposed between the motor and the pinion.
Here, in a case where the shift lever is configured to press a specific portion between the motor and the one-way clutch to push out the pinion, this specific portion can be prevented from being caused to rotate at a high speed while the starter is in the overrun state, because the one-way clutch blocks torque transmission from the engine to the starter. However, in a different case where the shift lever is configured to press a different specific portion between the one-way clutch and the pinion to push out the pinion, this portion is caused to rotate at high speed by the engine torque while the starter is in the overrun state. In the latter case, the friction between the shift lever and the specific portion becomes very large when there occurs the overrun state, and it cannot be reduced sufficiently by adopting the above described structure in which a hole is made in the end portion of the shift lever, and the hole is filled by grease. Accordingly, there has been a problem that the shift lever, which is generally made of a thermoplastic resin, may be worn and deformed by friction heat at its end portion.
Although the friction between the shift lever and the specific portion when there occurs the overrun state can be effectively suppressed by coating the end portion of the shift lever with a heat-resistant and wear-resistant material, there arises another problem in this case that the production cost of the shift lever becomes considerably high, because resin is very difficult to coat. It may occur that the shift lever is made of metal which is easy to coat. However, the production cost of the shift lever is still high in this case compared to the case of the shift lever being made of resin.